In communication base station devices of various standards, such as the global system for mobile communications (GSM, Global System for Mobile Communications), the code division multiple access (CDMA, Code Division Multiple Access), the wideband code division multiple access (WCDMA, Wideband Code Division Multiple Access), the time division-synchronous code division multiple access (TD-SCDMA, Time Division-Synchronous Code Division Multiple Access), the worldwide interoperability for microwave access (WiMax, Worldwide Interoperability for Microwave Access) and the long term evolution (LTE, Long Term Evolution), a power amplifier is required to amplify a signal, and the performance specification and engineering specification of a radio base station product directly depend on the performance of the power amplifier. Working in a nearly saturated state with high power, a power amplifier (especially, a final-stage power amplifier) is easily burned and may cause a series of serious consequences, for example, directly cause that a communication base station fails to work normally to interrupt a communication service, and the cost increases as a part of boards become unrepairable and thus scrapped.
In the prior art, the foregoing technical problem is mainly solved by detecting a final-stage signal amplitude to trigger the switching off of a preceding stage amplified circuit. The technical solution has a certain effect of protecting the power amplifier when an abnormal signal, such as a signal with continuous high power or a signal with a standing wave, occurs in the circuit, but when an abnormal signal, such as a burr and a pulse, occurs in the circuit, the technical solution has no effect of protecting the power amplifier.